A remarkable life story doesn’t automatically make a good documentary. Certainly the journey of Rachel Flowers, a blind musician and composer, is impressive, but “Hearing Is Believing,” a documentary about her, doesn’t put enough effort into giving her tale depth and context.

Ms. Flowers, now 23, was born 15 weeks premature, and among the complications was the loss of her eyesight. Yet, as a toddler, she demonstrated profound musical ability, and she was soon adept on keyboards, flute and other instruments. A measure of YouTube fame followed.

The film, by Lorenzo DeStefano, chronicles her musical development, but haphazardly, sometimes seeming more promotional than exploratory. We learn only a little about Ms. Flowers’s creative process and the difficulties she and her family faced over the years.

The film also doesn’t make much effort to put her achievements in historical context. A number of skilled musicians, some of them household names, have been blind or faced other physical challenges. Despite a cameo by Stevie Wonder, that goes largely unacknowledged. It would have been nice at least to hear Ms. Flowers’s thoughts on where she fits in this chain of rare talents. More outside assessments of her music also would have been welcome.

After an aimless hour, the film eventually gets some traction with a segment in which Dweezil Zappa brings Ms. Flowers onstage during one of his concerts to perform works by his father, Frank Zappa. It’s the climax of this film, but really Ms. Flowers’s career is just beginning. There might be a better documentary to be made about her some years in the future.